Empirical Relation for Electronic and Optical Properties of Binary Tetrahedral Semiconductors

The concept of ionicity has been developed by Phillips and Van Vechten from the dielectric analysis of the semiconductors and insulators to evaluate various bond parameters of binary tetrahedral (AIIBVI and AIIIBV) semiconductors. In this paper, an advance hypothesis of average atomic number of the elements in a compound has been used to evaluate intrinsic electronic and optical parameters such as ionic gap (Ec), average energy gap (Eg), crystal ionicity (fi) and dielectric constant (ϵ) of binary tetrahedral semiconductors.

X-Ray spectrometric studies using thin silicon crystals. Advantages and applications

This paper presents the peak-to-background ratio improvement, which can be achieved in PIXE and XRF applications by the use of thin crystal detectors. This improvement becomes apparent in the presence of an intense γ-ray source, which can be produced either after proton irradiation of a sample (PIXE), or after the deexcitation of the radionuclide in Radioisotope induced XRF analysis (RIXRF). In order to study theoretically the energy response of a silicon crystal in the X-ray energy region with respect to its thickness and the energy of the incident yradiation, a Monte-Carlo simulation was performed. Experimentally, two detectors having crystal thickness of 300 urn and 3 mm respectively were employed in specific analytical applications of PIXE, PIXE induced XRF and RIXRF techniques. The peak-to-background ratios obtained for various characteristic X-rays were compared between the two detectors. The performance of the two detectors was also compared in monochromatic XRF analysis of samples with low average atomic number matrix content.

Methods for Conducting Electron Backscattered Diffraction (EBSD) on Polycrystalline Organic Molecular Thin Films

Electron backscattered diffraction (EBSD) is a technique regularly used to obtain crystallographic information from inorganic samples. When EBSD is acquired simultaneously with emitting diodes data, a sample can be thoroughly characterized both structurally and compositionally. For organic materials, coherent Kikuchi patterns do form when the electron beam interacts with crystalline material. However, such patterns tend to be weak due to the low average atomic number of organic materials. This is compounded by the fact that the patterns fade quickly and disappear completely once a critical electron dose is exceeded, inhibiting successful collection of EBSD maps from them. In this study, a new approach is presented that allows successful collection of EBSD maps from organic materials, here the extreme example of a hydrocarbon organic molecular thin film, and opens new avenues of characterization for crystalline organic materials.

Preparation and Thermal/Fast Neutron Shielding Properties of Novel Boron Containing Ore Composites

Four novel boron containing ores/epoxy composites were prepared by using nature ludwigite green ore (NLGO), artificial ores including boron containing iron ore concentrate (BCIOC), boron rich slag (BRS) and boron mud (BM) as neutron absorbers, which were obtained by dressing from NLGO, blast furnace separation from BCIOC and borax production, respectively. The microstructure of the composites was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR). Shielding properties of the composites against thermal and Cf-252 fast neutron were measured. Factors affecting the shielding properties were investigated. Energy deposition, absorbed dose and half value layers of the composites against neutron penetration were simulated by Monte Carlo method, and a simulated function was obtained. The results showed that the composites were compact and the particles of ores were homogeneous. Ascending boron mole numbers per unit volume (nB) in the composites can obviously enhance the macroscopic absorbing cross section (Σthermal) and improve the shielding properties for thermal neutron. The relationship of Σthermal and nB follows the equation of Σthermal=0.218+450.490nB. And the relationship of average atomic number (Z) of boron containing ores composites and the macroscopic removal cross section for fast neutron follows the equation of Σremoval=0.042exp (-Z/5.70)+0.032. Enhancement of the shielding abilities against Cf-252 fast neutron can be achieved by using the composites with low average atomic number.